On planes that is. Pre-911 I had a stewardess ask me to put away my needles when it was time for take-off/landings in case I "hurt myself." I guess now a days, I'd use them to "hurt others." It's more likely I'd use my ballpoint pen or tweezers to hurt someone then my knitting needles. :P
I can only read so much on a plane then I go crazy, I really miss knitting when I fly!